1. Field of the Invention
The present invention relates to a scanning image displayer applicable for projectors and mobile projectors, and more particularly to an ultracompact scanning image displayer scanning a laser beam with a minute deflecting mirror to display an image on a surface onto which the laser beam is projected. Further, the present invention relates to a mobile phone, a mobile information processor such as a notebook PC, a mini notebook PC and a mobile PCs, and a mobile imager such as a digital camera and digital video camera.
2. Description of the Background Art
Compact scanning image displayers, i.e., laser projectors deflectively scanning a laser beam from side to side and up and down with a minute deflecting mirror and controlling an emission power of the laser beam at the same time to display images are now being developed. Since the laser projectors have much smaller sizes than conventional projectors having light sources, image display panels, and projection lenses, they are expected to be installed in mobile phones, mobile image processors such as notebook PCs, mini notebook PCs and mobile PCs, and mobile imagers such as digital cameras and digital video cameras.
However, they are still too large for practical use, e.g., the current OPT module has a size of from 4 to 6 cc, and particularly when they are installed in mobile phones their thickness of about 7 mm is a major hurdle.
Japanese Patent No. 4174420 shows a basic light path configuration of a laser projector in FIG. 14, in which a beam emitted from a laser light source is projected onto a screen through a first mirror deflecting in a main scanning direction and second mirror deflecting in a sub-scanning direction to form an image. The laser light source is a monochromatic light source, and not a color light source.
Japanese published unexamined application No. 2008-275930 synthesizes colors with a dichroic prism before a deflecting mirror in FIG. 1, in which W (white) is added besides the three primary colors R (red), G (green) and B (blue), but W is not indispensable. Further, it is considerably difficult to synthesize R, G, B, and W with a dichroic prism.
Japanese published unexamined application No. 2009-003429 synthesizes colors with an X prism and uses a two-dimensional deflecting mirror in FIG. 22. The X prism and the two-dimensional deflecting mirror considerably downsize the projector.
Japanese published unexamined application No. 2009-122455 discloses a configuration including two color laser light sources R and G in a CAN in FIG. 3, in which light paths can be shortened more than the projector including three color laser beams in separate CANS. The G laser is a combination of an infrared laser and a SHG generating a second harmonic wave in FIG. 3. Thus is because an LD of G suitable for projector applications is currently unobtainable, and an LD of G is thought to replace the combination in future. In addition, providing a condenser lens after a deflecting mirror is not indispensable.
Japanese published unexamined application No. 2006-186243 discloses a 1CAN3LD type including three color laser light sources R, G, and B in a CAN. This is, so to speak, an ultimate compact projector including only one light source (1CAN3LD), one condenser lens (CL) and one two-dimensional deflecting mirror. This is a very simple configuration, but includes difficult technologies to realize, such as 1CAN3LD.
As mentioned above, various light paths have been considered, and the deflecting mirrors are commonly arranged diagonally to a beam optical axis. This seems natural because the beam is reflected, but is a large hurdle to overcome to achieve greater compactness of the projector.
In consideration of downsizing the scanning image displayer (laser projector), two single-deflection deflecting mirrors in Japanese Patent No. 4174420 and Japanese published unexamined application No. 2008-275930 are noticeably disadvantageous, whereas a two-dimensional drive deflecting mirror is definitely used for a laser projector aiming at compactness.
FIG. 11 is a schematic view illustrating a principled configuration example of a two-dimensional drive deflecting mirror.
On a deflecting mirror substrate 12, a sub-scanning power generator 12d, a sub-scanning rotational axis 12b, a main scanning power generator 12c and a main scanning rotational axis 12a are connected with each other in this order from the outside in, and a deflecting mirror 12M is located at the center. The power generators 12d and 12c may be a solenoid-operated system, a piezo system, or other. Any of them needs a certain level of size, and the rotational axes 12a and 12b need a certain length as well, although depending on rotational angles and speeds. Only the deflecting mirror 12M at the center is optically necessary, but the deflecting mirror substrate 12 needs to be several times larger than the deflecting mirror 12M to two-dimensionally drive the deflecting mirror 12M. Although depending on the performance required for the deflecting mirror, the deflecting mirror substrate 12 needs to be at least five times larger in a main scanning direction and four times larger in a sub-scanning direction than the deflecting mirror 12M. This largely affects a total thickness of the scanning image displayer (laser projector) and is a barrier against thinning.
The two-dimensional deflecting mirror needs to be located in a direction to be thinner to thin the laser projector. However, when the two-dimensional deflecting mirror is located in a direction to be thinner, a reflection surface of the two-dimensional deflecting mirror and a optical axis of the laser beam from a light source become parallel to each other, and the laser beam does not enter the reflection surface of the two-dimensional deflecting mirror.
Therefore, a beam splitter shown in FIG. 16 (a) is typically used when the laser beam and the reflection surface are parallel to each other. As shown in FIG. 16 (a), the beam splitter bends the laser beam at a right angle at a separation surface (45° surface) and directs the beam to the reflection surface. The laser beam after being reflected is transmitted through the separation surface to be taken out.
Since the beam splitter needs to have a separation surface having both transmissivity and reflectivity, it may be simply a half mirror. However, in order to avoid light quantity loss, a so-called deflection beam splitter having a deflection separation film as a separation surface is used, when deflection status needs to change with reciprocation on a light path with a combination of a γ/4 plate (quarter wave plate), etc.
Since the beam splitter can bend the beam at a right angle and direct the beam to the two-dimensional drive deflecting mirror, the two-dimensional drive deflecting mirror can be located parallel to the optical axis and it may be thought that the laser projector can be thinner, but this is impractical. This is because the laser beam is oscillated by the two-dimensional drive deflecting mirror in the laser projector.
As shown in FIG. 13 (a), when the laser beam is not oscillated by the mirror, the beam splitter has only to have a size of a beam diameter+α. However, in the laser projector, as shown in FIGS. 13 (b) and 13 (c), all the laser beams oscillated by the two-dimensional drive deflecting mirror need to have such sizes as can be included in the beam splitter, and not only the width but also the thickness enlarge. Therefore, even the beam splitter cannot thin the laser projector.
For these reasons, a need exists for a scanning image displayer having such a thickness as can be installed in mobile phones.